JP4014073B2 - Two-chamber wet flue gas desulfurization system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wet flue gas desulfurization apparatus that removes sulfur dioxide (SO ₂ ) in exhaust gas discharged from a combustion apparatus such as a boiler. In particular, the exhaust gas is directed upward by installing a partition plate inside an absorption tower. In a two-chamber desulfurization device divided into two gas-liquid contact parts, a flowing upward flow region and a downward flowing region flowing downward, it has the functions of preventing gypsum accumulation in the circulation tank and improving the oxidation performance of calcium sulfite. The present invention relates to a two-chamber wet flue gas desulfurization apparatus.
[0002]
[Prior art]
In thermal power plants and the like, sulfur oxides in exhaust gas generated by the combustion of fossil fuels, especially SO ₂ is one of the main causes of environmental problems such as air pollution and acid rain. The desulfurization system that removes sulfur oxides in exhaust gas is mainly a wet method based on the limestone-gypsum method, and among them, the most reliable and reliable spray method is adopted worldwide.
[0003]
FIG. 6 shows a conventional technology of a two-chamber type wet flue gas desulfurization apparatus that adopts a spray system to reduce costs. The wet flue gas desulfurization apparatus mainly includes an absorption tower body 1, an inlet duct 2, an outlet duct 3, a partition plate 4, an absorbing liquid circulation pump 5, a circulation tank 7, a stirrer 8, an air blowing pipe 9, a mist eliminator 10, and an absorption. The liquid discharge pipe 11, the exhaust gas upward flow region 12, the exhaust gas downward flow region 13, the circulation pipe 14, the spray header 15, the spray nozzles 16 to 17, etc.
[0004]
A plurality of spray nozzles 16 and 17 are installed in a cross section orthogonal to the gas flow, and a plurality of stages are installed in the gas flow direction. The stirrer 8 and the air blowing pipe 9 are installed in a circulation tank 7 in which an absorbing liquid slurry 6 (hereinafter sometimes simply referred to as slurry) stays, and a mist eliminator 10 is installed in the outlet duct 3.
[0005]
The exhaust gas discharged from the boiler is introduced from the inlet duct 2 into the absorber tower body 1 in a substantially horizontal direction by a desulfurization fan and is discharged from the outlet duct 3. Many spray towers using a spray system discharge exhaust gas introduced from the lower part of the absorption tower from the top of the tower in order to bring the exhaust gas and the absorption liquid 6 into countercurrent contact. However, the prior art shown in FIG. Since the partition plate 4 is installed and the outlet duct 3 is provided at substantially the same height as the inlet duct 2, the exhaust gas introduced from the inlet duct 2 is blocked by the partition plate 4 and rises in the upflow region 12. After reversing at the top of the tower, the downflow region 13 is lowered.
[0006]
Meanwhile, in the upward flow region 12 and the downward flow region 13, the absorption liquid 6 containing calcium carbonate sent from the absorption liquid circulation pump 5 is atomized and sprayed from the spray nozzles 16 and 17 provided in the respective areas. Gas-liquid contact between the absorbing liquid 6 and the exhaust gas is performed. At this time, the absorbing liquid 6 selectively absorbs SO ₂ in the exhaust gas and generates calcium sulfite. Of the absorbing liquid 6 that has produced calcium sulfite, one having a small droplet diameter is accompanied by the exhaust gas and collected by a mist eliminator 10 provided in the outlet duct 3. Others with larger droplet diameters once accumulate in the circulation tank 7 and are stirred by an oxidizer stirrer 8 to produce calcium sulfate (gypsum) by oxygen in the bubbles 19 supplied from the air blowing tube 9. To do. A foam layer 18 is formed on the upper layer of the slurry 6 in the circulation tank 7. A part of the absorption liquid 6 in the circulation tank 7 in which calcium carbonate and gypsum coexist is sent again to the spray nozzles 16 and 17 by the absorption liquid circulation pump 5, and a part of the absorption liquid treatment is not shown through the absorption liquid extraction pipe 11.・ Sent to gypsum recovery system.
[0007]
The main purpose of the oxidizing stirrer 8 is to oxidize calcium sulfite, but it also serves to prevent gypsum deposits in the circulation tank 7. However, the number of stirrers 8 is determined by the amount of oxygen necessary for the oxidation of calcium sulfite, and the number of the stirrers 8 can provide sufficient power to stir the absorbent 6 so that gypsum does not necessarily accumulate at the bottom of the circulation tank 7. Not a number.
[0008]
Further, since most of the SO ₂ absorbed by the absorption tower body 1 is absorbed by the upflow region 12, the concentration of calcium sulfite in the absorbing liquid 6 falling from the upflow region 12 to the circulation tank 7 is downflow. It is about 3 to 10 times higher than that in the absorbing liquid 6 falling from the region 13. The absorption liquid 6 containing calcium sulfite at a high concentration on the upflow region 12 side is oxidized during the residence time until it is sucked into the circulation pump 5. The absorption liquid 6 that has dropped near the partition plate 4 is closer to the absorption port of the absorption liquid circulation pump 5 than the absorption liquid 6 that has dropped near the inlet duct 2, and the absorption liquid 6 having a high calcium sulfite concentration is circulated in a short time. 5 and it is difficult to obtain a residence time for complete oxidation of calcium sulfite.
[0009]
[Problems to be solved by the invention]
In the above prior art, sufficient stirring force cannot be obtained for prevention of gypsum deposition in the circulation tank 7, and gypsum accumulates in the central portion of the circulation tank 7 where the absorption liquid 6 is not sufficiently stirred. Further, when gypsum that has accumulated and solidified is sucked into the circulation pump 5, the spray nozzles 16 and 17 are clogged and the circulation pump 5 is damaged.
[0010]
Further, in the prior art, sufficient consideration is not given to the oxidation of calcium sulfite in the absorption liquid 6 in the circulation tank 7. If calcium sulfite remains in the absorption liquid 6 sprayed from the circulation pump 5 to the absorption tower body 1, there is a problem that the desulfurization performance in the absorption tower is reduced and scaling to the spray nozzles 16, 17 and the tower wall is caused.
[0011]
The object of the present invention is to prevent gypsum from accumulating at the bottom of the circulation tank, and to completely oxidize high-concentration calcium sulfite in the absorbent slurry 6 on the side of the upflow region of the exhaust gas in the absorption tower in the circulation tank. Accordingly, there is provided a wet flue gas desulfurization apparatus that prevents clogging of a spray nozzle, breakage of a circulation pump, deterioration of desulfurization performance, and occurrence of scaling, and has high reliability and stable operation.
[0012]
[Means for Solving the Problems]
The object of the present invention is to provide an inlet duct for introducing exhaust gas discharged from a combustion apparatus including a boiler in a substantially horizontal direction, and an outlet duct for discharging purified exhaust gas in a substantially horizontal direction. An exhaust gas flow path is provided between the two, and an inlet duct is provided by providing a vertical partition plate having an opening on the ceiling side for dividing the exhaust gas flow path into two chambers on the inlet duct side and the outlet duct side. An upward flow region where the exhaust gas introduced from the top flows in an upward direction and a downward flow region where the exhaust gas flows downward toward the outlet duct after reversing at the opening on the ceiling side, a spray nozzle is installed in each region, and the spray nozzle Absorber for treating sulfur oxides in exhaust gas, arranged so that the absorbent slurry ejected from the gas and the exhaust gas are in countercurrent contact in the upward flow region and in parallel flow contact in the downward flow region In two-chamber type wet flue gas desulfurization apparatus and a circulating tank for storing the absorbing solution slurry ejected from spray nozzles below the absorption tower,
The lower end portion of the partition plate is immersed in the absorbing liquid in the circulation tank, and the partition plate is below the half of the liquid depth of the absorbing liquid slurry in the circulation tank and the lower end of the partition plate. The downward flow partitioned by the partition plate from the cross-sectional area perpendicular to the gas flow direction of the downward flow region inside the absorption tower in which the exhaust gas flows downward is provided with an absorbent liquid slurry circulation portion between the bottom portion and the bottom of the circulation tank This is solved by a two-chamber wet flue gas desulfurization apparatus that reduces the cross-sectional area opposite to the cross-sectional area perpendicular to the gas flow direction of the downflow region of the slurry reservoir in the circulation tank located in the lower part of the region .
[0013]
[Action]
According to the two-chamber wet flue gas desulfurization apparatus of the present invention, the slurry is placed between the lower end of the partition plate and the bottom of the circulation tank and below the half of the liquid depth of the absorbent slurry in the circulation tank. By providing the flow part, the gypsum particles are accompanied by the flow of the slurry and flow through the slurry flow part, so that the gypsum can be prevented from being deposited on the bottom of the circulation tank.
[0014]
Further, since the size of the slurry circulation part is set so that the average flow rate of the absorbent slurry in the absorption liquid slurry circulation part in the circulation tank is 0.5 to 4 m / second, occurrence of scaling is prevented. Can do.
[0015]
Further, from the cross-sectional area of the gas flow direction of the downward flow region inside the absorption tower which the exhaust gas flows downward, the downward flow region of the reservoir of the slurry circulating tank positioned in the downward flow region downward partitioned by the partition plate By reducing the cross- sectional area opposite to the cross- sectional area in the direction perpendicular to the gas flow direction, the volume in the circulating tank on the upflow region side inside the absorption tower is increased to increase the absorption liquid slurry containing calcium sulfite at a high concentration. Side descent rate can be reduced, sufficient residence time can be obtained, and high concentrations of calcium sulfite can be completely oxidized in the circulation tank.
[0016]
In addition, when a large amount of bubbles are generated due to the amount of oxidizing air remaining in the slurry in the circulation tank located below the upflow region where the exhaust gas in the absorption tower flows upward, the partition plate part immersed in the circulation tank in if provided oxidizing air flow hole, can be circulated oxidizing air into the slurry in the circulating tank located below the downward flow area within the absorption tower from the flow holes, the upflow area The amount of oxidizing air in the slurry in the circulation tank below the side can be adjusted.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment according to the present invention, and members having the same functions described in FIG. FIG. 1 shows that the slurry circulation part below the lower end of the partition plate 4 in the circulation tank 7 is in contact with the bottom part of the circulation tank 7 so that the height thereof is 1/5 of the liquid depth, thereby passing through the slurry circulation part. The side view of the absorption tower which made the average slurry flow velocity to perform 0.5 m / sec is shown. FIG. 2 is a graph showing the relationship between the amount of gypsum deposited at the bottom of the tank 7 and the average flow velocity of the slurry 6 passing through the slurry circulation section. FIG. 3 shows an example in which the cross-sectional area of the slurry reservoir in the circulation tank 7 at the bottom of the downflow region is reduced so that the cross-sectional area of the downflow region of the absorption tower main body where the exhaust gas flows downward is 1/5. It is.
[0018]
In the embodiment shown in FIG. 1, the height of the slurry circulation portion between the lower end portion of the partition plate 4 immersed in the circulation tank 7 and the bottom portion of the circulation tank 7 is about 1 / th of the liquid depth from the bottom portion of the tank 7. 5 is different from the prior art in that the average flow velocity of the absorbent slurry 6 passing through the slurry 6 flow portion is 0.5 m / sec. The absorbing liquid 6 falling to the upflow region side 12 descends the circulation tank 7, passes through the slurry circulation section at the lower end of the partition plate 4, and is sucked into the absorbing liquid circulation pump 5.
[0019]
At this time, accumulation of gypsum can be prevented by setting the cross-sectional area of the slurry circulation portion in consideration of the average slurry flow velocity passing through the slurry circulation portion so that the gypsum particles flow along with the flow of the slurry 6. In the two-chamber wet flue gas desulfurization apparatus, the average flow velocity of the slurry 6 passing through the slurry circulation part is about 0.1 m / second or less.
[0020]
FIG. 2 shows the relationship between the average flow rate of the slurry 6 passing through the slurry circulation part and the amount of gypsum deposited on the bottom of the tank 7. The amount of gypsum deposited is expressed as a relative amount based on the time when the flow rate is 0.1 m / second or more. 2 that the amount of gypsum deposited decreases when the average flow velocity of the slurry 6 passing through the slurry circulation section is high. Desirably, gypsum deposition can be prevented when the average slurry flow rate is 0.5 m / second or more. Moreover, if the average slurry flow velocity which passes a slurry distribution part is raised, the load of the motive power of the pump 5 which circulates them to an absorption tower will become high, a circulation amount will reduce and desulfurization performance will fall. Considering these, it is desirable that the average slurry flow velocity in the circulation part of the partition plate 4 in the circulation tank 7 is 0.5 to 4 m / sec.
[0021]
In the embodiment shown in FIG. 3, the gas flow direction in the circulation tank 7 below the downflow region 13 is reduced to 1/5 times the cross-sectional area of the downflow region 13 of the absorber main body where the exhaust gas flows downward. It differs from the prior art in that the cross-sectional area is reduced. If the cross-sectional area in the gas flow direction on the upflow region 12 side in the circulation tank 7 is increased, the descent speed of the slurry 6 decreases, so that the residence time in the circulation tank 7 on the upflow region 12 side becomes longer. Calcium sulfite can be oxidized more completely, but the cross-sectional area in the gas flow direction in the circulation tank 7 on the downflow region 13 side is reduced, and the descending speed of the slurry 6 in the downflow region 13 is increased. The residence time is shortened. The slurry 6 on the downflow region 13 side has calcium sulfite that cannot be ignored, and a residence time corresponding to its oxidation is required. Further, as the descending speed of the slurry 6 increases, the slurry in the circulation tank 7 is increased. 6, the ratio of the oxidized air absorbed in the circulation pump 5 increases, and the cavitation of the pump 5 and the decrease in the circulation amount of the slurry 6 occur. Therefore, the direction of gas flow in the circulation tank 7 on the upflow region 12 side The upper limit of the cross-sectional area is limited. In consideration of these, the inside of the circulation tank 7 partitioned by the partition plate 4 located below the downflow region 13 from the cross-sectional area in the gas flow direction of the downflow region 13 of the absorption tower body 1 in which the exhaust gas flows downward. The cross-sectional area in the gas flow direction is desirably 1 to 1/10 times.
[0022]
The embodiment shown in FIG. 4 is shown in FIG. 1 in that a stirrer 20 with an air blowing pipe 21 is installed on the wall surface of the circulation tank 7 above the suction port of the circulation pump 5 in the embodiment shown in FIG. Different from the embodiment. In order to increase the average slurry flow velocity passing through the slurry circulation portion between the lower end portion of the partition plate 4 and the bottom portion of the circulation tank 7, the area of the slurry circulation portion is reduced and the slurry stirring power of the stirrer 8 is decreased. Then, the oxidizing air supplied from the stirrer 8 is kept on the upflow region 12 side of the circulation tank 7. Further, since the calcium sulfite in the slurry 6 on the downflow region 13 side has a low concentration, a long oxidation time is not required, and it is not sucked into the circulation pump 5, and the cavitation of the pump 5 due to the suction of the bubbles 22, the circulation amount of the slurry 6 Can be prevented from decreasing and fluctuating.
[0023]
The embodiment shown in FIG. 5 is the embodiment shown in FIGS. 1 and 4 in that an oxidation air circulation hole 23 is provided in the partition plate 4 portion immersed in the circulation tank 7 in the embodiment shown in FIG. Different from form. When a large amount of foam layer 18 is generated due to the amount of oxidizing air remaining in the slurry 6 in the circulation tank 7 on the upflow region 12 side partitioned by the partition plate 4, it is partitioned by the partition plate 4 from the circulation holes 23. By allowing the oxidizing air to flow through the slurry 6 in the circulating tank 7 on the downflow region 13 side, the amount of oxidizing air remaining in the slurry 6 in the circulating tank 7 on the upflow region 12 side of the circulating tank 7 is reduced. Can be adjusted.
[0024]
In addition, the invention shown by said embodiment can acquire an effect irrespective of a round shape and a square-shaped circulation tank.
[0025]
【The invention's effect】
According to the first aspect of the present invention, it is possible to prevent gypsum from accumulating at the bottom of the circulation tank, so that the accumulated and solidified gypsum is sucked into the circulation pump to prevent clogging of the spray and damage to the pump. be able to. In addition, since the slurry with a high calcium sulfite concentration falling from the upflow region can be completely oxidized in the circulation tank, it is possible to reduce the desulfurization performance in the absorption tower and prevent the occurrence of scaling, resulting in high reliability. It becomes a wet type flue gas desulfurization device that is high and capable of stable operation.
According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, in the circulation tank located below the downflow region in the absorption tower from the oxidation air circulation hole provided in the partition plate portion. Oxidizing air can be circulated in the slurry, and the amount of oxidizing air in the slurry in the circulation tank below the upflow region can be adjusted.
[0026]
In addition, since the slurry with a high calcium sulfite concentration falling from the upflow region can be completely oxidized in the circulation tank, it is possible to reduce the desulfurization performance in the absorption tower and prevent the occurrence of scaling, resulting in high reliability. It becomes a wet type flue gas desulfurization device that is high and capable of stable operation.
[Brief description of the drawings]
FIG. 1 is an embodiment according to the present invention, and shows a side view of an absorption tower provided with a circulation part so that an average slurry flow velocity of a slurry circulation part in a partition plate in a circulation tank is 0.5 m / second. is there.
FIG. 2 is a graph showing the relationship between the amount of gypsum deposited on the bottom of the tank and the average flow velocity of the slurry passing through the distribution part of the partition plate.
FIG. 3 is an embodiment of an absorption tower in which the cross-sectional area in the circulation tank at the lower part of the absorption tower is reduced to be 1/5 times the cross-sectional area of the downflow region of the absorption tower main body where the exhaust gas flows downward.
4 is an embodiment in which a stirrer with an air blowing pipe is installed on the inlet of the circulation pump in the embodiment of FIG.
5 is an embodiment in which oxidized air circulation holes are provided in the partition plate portion immersed in the circulation tank in the embodiment shown in FIG.
FIG. 6 is a side view of an absorption tower in a conventional two-chamber wet flue gas desulfurization apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Absorption tower body 2 Inlet duct 3 Outlet duct 4 Partition plate 5 Absorbing liquid circulation pump 6 Absorbing liquid (slurry)
7 Circulating tank 8, 20 Stirrer 9, 21 Air blowing pipe 10 Mist eliminator 11 Absorbing liquid discharge pipe 12 Exhaust gas upflow area 13 Exhaust gas downflow area 14 Circulation pipe 15 Spray header 16, 17 Spray nozzle 18 Foam layer 19, 22 Bubble 23 Air flow hole for oxidation

Claims (2)

An inlet duct for introducing the exhaust gas discharged from the combustion apparatus including the boiler in a substantially horizontal direction and an outlet duct for discharging the purified exhaust gas in a substantially horizontal direction are provided, and an exhaust gas flow path is provided between the inlet duct and the outlet duct. Exhaust gas introduced from the inlet duct faces upward by providing a vertical partition plate with an opening on the ceiling side for dividing the exhaust gas flow channel into two chambers on the inlet duct side and the outlet duct side An upflow region flowing in the ceiling and an opening on the ceiling side, and then a downward flow region in which exhaust gas flows downward toward the outlet duct is formed. A spray nozzle is installed in each region, and an absorbing liquid slurry is ejected from the spray nozzle. An absorption tower for treating the sulfur oxide in the exhaust gas, which is arranged so that the exhaust gas is in countercurrent contact in the upflow region and in parallel contact in the downflow region;
A circulation tank for storing an absorption liquid slurry ejected from a spray nozzle below the absorption tower;
In a two-chamber wet flue gas desulfurization device equipped with
The lower end portion of the partition plate is immersed in the absorbing liquid in the circulation tank, and the partition plate is below the half of the liquid depth of the absorbing liquid slurry in the circulation tank and the lower end of the partition plate. An absorbent slurry circulating part is provided between the part and the bottom of the circulation tank ,
From the cross-sectional area perpendicular to the gas flow direction of the downflow region inside the absorption tower in which the exhaust gas flows downward, the gas in the downflow region of the slurry reservoir in the circulation tank located below the downflow region partitioned by the partition plate A two-chamber wet flue gas desulfurization apparatus characterized in that a cross-sectional area facing the cross-sectional area perpendicular to the flow direction is reduced .   The two-chamber wet flue gas desulfurization apparatus according to claim 1, wherein an oxidation air circulation hole is provided in a partition plate portion immersed in the circulation tank.

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